Purpose: :
Abnormal visual experience results in amblyopia, strabismusand poor control of eye growth. A number of studies have consideredprescribing spectacles for young hyperopes in an attempt toprevent permanent visual abnormality. Our goal was to estimatethe habitual retinal defocus of infants and children as a functionof age, refractive error and acuity to determine the levelsof refractive error at which visual experience becomes ‘abnormal’.

Methods: :
Infants and children from 6 months to 8 years of agewere recruited in a clinical environment. None of the childrenhad had any prior treatment or spectacles. Age, monocular acuity,accommodative accuracy (Nott retinoscopy and a cartoon at 50cm) and cycloplegic refractive error were all recorded afterthe parents had given informed consent. The acuities were measuredusing age–appropriate clinical techniques and convertedto Snellen equivalents for the purpose of consistency.

Results: :
The acuity and refractive error distributions wereconsistent with the published literature. Using a multiple regressionanalysis, the subjects’ ages and estimates of acuity werenot significantly related to their measured accommodative accuracyin this group of patients. Subjects with 5D or less of hyperopicisoametropia exhibited accommodative lags of no more than 1D.Subjects with larger amounts of hyperopia typically exhibitedmuch larger lags, indicative of significant blur.

Conclusions: :
The data suggest that a population–basedrefractive error function for abnormal visual experience canbe derived from measures of accommodative accuracy using naturalisticstimuli. This empirical analysis can be used to target the prescribingof preventative spectacle correction.